As of October 1, Medicare stopped paying for medical expenses due to “never events”—so called because they indicate preventable mistakes that should never happen, such as leaving objects inside patients after surgery and operating on the wrong body part. The new policy also stipulates that patients themselves cannot be billed directly for such errors.

But the failure to get reimbursed by insurers may not prevent seemingly careless medical mistakes.

A study published in the Annals of Surgery and reported by Reuters this week found that sponges and other instruments are miscounted at least once in every eight surgeries. Most of the time, instruments are found before any harm is done, but for one in every 5,000 surgeries, an instrument or sponge is left inside the patient.

In Oregon, the University Health Center Medical Director Ben Douglas explained the problem of detecting sponges: “It’s not like taking the top off a shoe box and just seeing everything at the same time.” Oregon Patient Safety Commission administrator, Jim Dameron recalled a demonstration where doctors were made to guess how many sponges were in a Jello-filled tank, the sides of which were opaque. Damerson said one doctor guessed there were five sponges, then “I stuck my hand in the Jell-O and I rummaged around and found three sponges.” In 2007, in Oregon, there were 15 incidents of objects being left behind in patients, based on voluntary reports. Oregon remains the only state where hospitals aren’t legally required to report mistakes.

The standard procedure for most hospitals involves manually counting tools and sponges before surgery begins and later, before an opening is sewn closed. Some hospitals do another check mid-way through the procedure, just before beginning to sew an opening. New devices such as sponges imbedded with radioactive chips, while expensive, would allow surgeons to detect items by passing a wand over the patient’s body.

And then there are wrong-site surgeries, another seemingly laughable error that can be devastating or even deadly. In the past year there have been three cases at two Rhode Island hospitals in which surgeons attempting to alleviate pressure from blood pooling next to patients’ brains drilled into the wrong side of their heads, the Providence Journal reports. Despite numerous attempts at establishing better procedures such as physically marking the surgical area, pausing for “time-outs” before surgery and using digital x-ray machines—to prevent the incident of x-rays being hung backward on screens —problems continue to occur, though at a much lower rate than forgotten objects.

The Providence Journal cited The Joint Commission’s estimates that a wrong-site incident takes place every 113,000 surgeries. Researchers blame everything from the number of people involved in surgery to the aura of intimidation radiated by surgeons preventing others from voicing their doubts. Ultimately, as H. John Keimig, former president of St. Joseph’s Hospital Services in Rhode Island explained, “It’s easy for an academician in some ivory tower to write some best-practice protocol. When you get on the front lines of battle, so to speak, and you’ve got adrenaline running and nerves frayed and people tired, those perfect systems just break down because of human frailties.”

The Los Angeles Times reported that between July and November 2007 there were 59 cases of objects left inside patients. In addition, at one hospital, St. Joseph’s in Los Angeles, there were three “wrong-site” cases within a year. In one case, an operation was performed on the wrong side of a patient’s head. Jim Lott, executive vice president of the Hospital Association of Southern California, said, “I’ve got to believe that St. Joseph’s is beside itself trying to figure out what’s not working.” The Joint Commission’s national voluntary reporting system receives eight wrong-site cases a month, 70 percent of which are fatal.

BNet cited a study in the Annals of Surgery regarding the RFID sponges and detection, noting the problem of human error: “If the scan is performed incorrectly (e.g., the wand is too far away from the skin to detect the sponges or the wand does not cover the entire surface area of the surgical site), retained sponges could be missed.”

However, in post-surgery surveys, some doctors complained that the device, a 12-inch wand that is attached to another “toaster-size” instrument, was “cumbersome.” Lead researcher Alex Macario told Science Daily, “The technology to achieve this is not there yet because tagging a small pair of steel scissors, or even a small sponge, has not been entirely worked out.” The RFID tag is larger than some surgical instruments and interferes with the function of others.

CMS, the Center for Medicare and Medicaid Services, provides a complete list of “never events” defined as “serious and costly errors in the provision of health care services that should never happen.” As of October 1, Medicare will no longer pay for hospital bills incurred as a result of these preventable mistakes. Other insurance agencies are expected to follow suit.